Control of railway trains



June 23, 1925.

W. J. UNDERWOOD CONTROL OF RAILWAY TRAINS 2 Sheets-$heet 1- Filed July 12 June 23, 1925. 1,543,461

W. J. UNDERWOOD CONTROL OF RAILWAY TRAINS- Fild July 12 1923 2 Sheets-Sheet 2 87%;.WWM

ATTX- Patented June 23, 1925. 7

\ 'WAL'IEER JOHN UNDERWOQD OF: LONDON, ENGLAND.

CONTROL OF RAILWAY f TRAINS.

Application filed July 12,

T aZZ whom it may cmzccrn:

Be it known thatlflvenrnn JOHN UN- nnnwoon, of 24 Stanley CrescentfNotting Hill London, YV. 11, England; a subject of the King of Greatllritain and Ireland, have invented certain new and-usetulllmprove me its inland Relating tothe Control of Railway Trains, of which the following i a saeciiication.

This invention relates to the control of trafiic on single track railways andhas for its object to provide means enabling a fool-- proof n ethcdloi' control similar to that ,described in my cmpcnding application Se rial No. 5398.3l1filed on the 28th February,

19 2, to be applied vithout requiring the m is I" the single-track sections lnt6l111G- (lists the various stations to be bonded, that 'is, to 'he made electrically continuous throughout each section.

"llhepresent improvement consists in the provision of an ,electronia gnet at each stetion normallyenergized and controlling the main operating circuits and so connected to to source of curr nt and to-appropriate portions of the track that on a train leavstation the electroinognet is 'do-enei d andopens the operating circuits coning: the shid station with the next staich the train is proceeding and oinagnet cannot again be enerse the said circuit nntilthe train rrives at the said no station, thus preventingflthe possibility of a second train beinadvertently star-ted, either "from the said next station in the opposite direction, or from the first mentioned station in the same direction until the single track sec- ,tion connecting the two stations has been completely cleared by the first train; but without requiring the rails of the single track section to'be bonded.

In order that the nature or" the invention may be clearlyunderstood an arrangement in "ACCOl'ClflllCG therewith w'illvnow re d ri-bed with reference to the accompanytil d i o p'rannna'ti c drawings in which 1 shows the connections according to the invention for one completestation end th two singletrack sections extending 1117, one in each direction;

l 2 an-eqfvlenatory diagram showing the cii'ect upon the circ when u' train from one station to the next sta track section"X .wi.th estation B on t 'i ightyan'd by as'lngle' track section Y with ;provided with contacts right hand side :and Yi'll'll contacts 15 and connected by awire v connected by a line wire 1923. Serial No: 650,984.

Fig; 3 showsan optional "detail which may be employed in connection with the invention.

Referring'to"the drawings, a station A is shown in" Fig. "1 connected by a single he a station C ,on'the' left.

The switchl in the signal cabin at'stetion'A. is usedin conjunctionwith the switch '2.in the signal cabin atstation B for the control oftraflic passing in both directions between stationsA and B along track sec-- 'tion X,. and the switch :in the signal'cabin at station A is used in conjunction "with "the switch lin the signal cabin at station 'Cfilor the control oi trailic pessing along;

track section'.Y in both directions between stations 'A and C. It-will of course be understood-"that the single track sections X and Y may be of any indefinite length,

' usually illIiOllIltlilglO at least several miles.

'For the purpose of illustration it will be assumed that the ti'afiic controlling devices which are to ibe'directly operated by means of the foolproof arrangement according;

*to my atoresaid pending applicationare of the nature of inoveable trip devices having a safety anda dangerposition and designed to produce signalling "indications on the passing trains,--or to stop ,a train if danger conditions prevail on the track ahead of the v train.

The traihc starting-from. branch track 5 at station A- towards station B is controlled b 1 a" track trio havin an ooeratinc coil 6 i D J and thetralhc starting from branch track 7 at station A-towardsstation C is controlled' a track trip having an operating coil 8.

"Similarly the traflic starting from branch 'track '9 at. station is controlled by means of a 'track'trip',liav1ng-an operating coil 10, and trailie starting from branch track '11 at station: U towards station A is controlled by means of a truck trip having an operating coil 12.

"The controlling switch 1 at station A 13 and 14% on the trio opcrating'coil 6 The other end of trip coil 10 is connected by a wire 19 to contact 21 on the right hand side of controlling switch 2 which is also provided on the same side with the co-act ing contact 20, and on the left hand side with contacts 22, 23. t

The controlling switch 3 at station A is provided on the right hand side with contacts 24, 25 and on the left hand side with contacts '26, 27. The contact 25 is connected by a wire 28 to one end of the trip operating coil 8, the other end of which is connected by a line wire 29 to one end of the trip operating coil 12 at station C. The other end of trip coil 12 is connected by a wire 30 to contact 32 on the right hand side of controlling switch 4 which is also provided on the same side with the co-acting contact 31, and on the left hand side with contacts 33, 34.

At station A in connection with controlling switch 1 a battery or other suitable source of current 35 is provided for supplyis provided for supplying current to the trip coil 8, the positive pole of this battery being connected by a wire 59 to the contact 24 of switch?) through the movable lower contact 60 on the core (31 of the solenoid 62 when the latter is energized. The negative pole of battery 58 is connected by a wire 63 to the earthed wire and earth 42. The contact 26 on the left hand side of switch 3 is connected to earth 42 through wires 64, 44, and upper contact 65 of the core 61 when the solenoid 62 is energized, the contact 65 being carefully insulated from the core 61 and thence froin the lower contact 60. The C011".

tact 27 .of switch 3 is connected to the line wire 29 by a wire 66.

At station 0 in connection with controlling switch 4, which must be used in co-operation with switch 3 at station A. to control the trafic on single track section Y, a battery G6 is provided for supplying current to trip coil 12. The positive pole of battery ing current to the trip coil 6, and the posi-a-66 is connected by a wire 67 to the contact tive pole of this battery is connected by a wire 36 to the contact 13 of switch 1 through the lower contact 37 connected to the core or armature 38 of the solenoid or electromagnet 39 when the latter is energized as shown in Fig. 1. The negative pole of bat tery 35 is connected to the earthed wire 4- by a wire 41, the wire 40 being connected to earth at 42. The contact 15 on the left hand side of controlling switch 1 is connected to earth 42 through wires 43 and 44 and through upper contact 45 of solenoid core 38 when the solenoid 39 is energized as shown, the contact 45 being carefully insulated from the said core and from lower con-- tact 37. The contact 16 of switch 1.is connected to the line wire 18 by a wire 46.

At station B in connection with controlling switch 2, which must be used in co-op eration with switch 1 at station A to control the trafiic on single track section X, a battery or other suitable source of current 47 is provided for supplying current to trip coil 10. The positive pole of battery 47 is connected by a wire 48 to the contact 20 of switch 2 through the lower contact 49 connected to the core or armature 50 of the sole noid or electromagnet 51 when the latter is energized The negative pole of battery 47 is connected by a wire 52 to the earthed wire 53 which is connected to earth at 54. The contact 22 on the left hand side of controlling switch 2 is connected to earth 54 through wires 55 and 53 and upper contact 56 carried by the core 50 of solenoid 51 when this is in energized condition, the said contact 56 being carefully insulated from the core 50 and thence from the lower con tact 49. The contact 23 of switch 2 is connected to the line wire 18 by a wire 57.

Referring again to station A, in connection with controlling switch 3 a battery 53 31 of switch 4 through the lower contact 68 on the core 69 of the solenoid 70 when this is energized. The negative pole of battery (36 is connected by a wire 71 to the earthed wire 72, which is connected to earth at 73. The contact 33 of controlling switch 4 is connected to earth 73 through wires 74 and 72 and upper contact 75 on the core 69 of solenoid 70 when this is energized, the contact 7 5 being carefully insulated from the core 69 and lower contact 68. The contact 34 of switch 4 is connected to the linewire 29 by a wire 76.

With the exception of the solenoids 39, 5'1, 62 and 70, and their operation by the ll'lOVQiTltlliiS of the trains as hereinafter explained, the apparatus described above, comprising the switches 1, 2, 3, 4, their contacts, and connections to the trip coils and to the line wires, is similar in arrangement and operation to the corresponding apparatus shown in Fig. 1 of my aforesaid pending application. It is therefore unnecessary to more ininutely describe the said parts herein. But in the present improveinent the return of all line circuits is through the earth and the bonding of the track rails of the single track sections is entirely dispensed with, the safety of the system being automatically effected by the trains by the following means.

At station A in connection with controlling switch 1 and solenoid 39 an additional battery 77 is provided the positive pole of which is connected to the windings of the solenoid by a wire 78, while the negative pole connected to earth 42 by the earthed wire 40 and a wire 79, preferably through a switch 80 the object of which will be pointed out hereinafter.

The solenoid 39 has two windings, one 81 of thick wire and relatively low resistanceyand the other 82 of thin wire andrelatively highresistance. The winding 81 is so designed and dimensioned'that its ain'- pere-turns are sufficient to lift the core 38 from its de-energized to its energized position when the said winding is directly connected between the'batte'ry 77 and earth: but the said winding 81 is unable to lift the core 38 if any considerable amount of resistance is connected in circuit therewith, such for instance as the resistance ofthe thin wire winding 82. The winding 82 is formed of a wire having-a cross sectional diameter which may be only a fraction, for examplev th, of thatof the-wire forming thewinding- 81 and is so dimensioned that its ampere-turns are sufficient to hold 'upthe core 38 when connected directly between the battery 77 and-earth, that is; without anyrelatively considerable amount of resistance being con nected in series therewith. To give numerical examples,- merely by way of illustration, the lifting winding 81 might be of copper wire having a resistance of approximately 6 ohms per mile; the holding winding 82 night he of copper wire having a resistance of approxi1nately'185 ohms per mile. The ampere-turns of winding 82 when connected directly between the battery 77 and earth must not in any'case' besuiiicient to lift the core 38 from its lower to its raised position but only tohold the core in the latter position after it-has been raised thereto by the thick wirewinding 81.-

The thick wire winding Slis connected by a wire 83 to a second line wire 8% extending to the next station'B, while the thin wire winding 82-is connected to wire 13 and thence to earth 412 through the upper contact 4-5 of solenoid 39 and wire a l when the said"-sole n0id is energized.

'ihe'positivepole-of the battery 77 is connected by a wire 85 to an outerdeng-th ofrail 86 leading from the single track section- X; to the branch track 7 at station A, and the rail 86 is also connected electrii .ally by awire 87 to'an outer length of rail 88 leadingfroin: the branch track?) at sta tion A to the single tracksecti-on X, the two rails 86 and 88 beingcarefullyinsulated from earth and defined by. track insulationof any usual kind as shown. The inner rail length 89 leading-to track 7 from the single track section X and theinner raillength 90v leading from branch track 5 to' the single track section X are connected electrically by a wire 91 and to earth at92'as shown. Adjacent to the hoine'endof the: rail-86 to be finally left by a train arrivingfat station A from station B isashortlength of rail 93 which is insulated: froniearth and from the adjacent rail 86 by track insulation as shown, thetrack insulation being :so arranged that as longas a wheel on an axle of a yehicle1sin -.contactwith.ra1l 93 the other'wheel at the opposite end of said axle will-bein contact with the rail 89 and thence with-earth 9 The rail'98 is'electrically connected 'to the line wire 8 1 by a 'wiie94, preferablythrough a switch 95-for a reason hereinafter explained.

Similar arrangements and connections to those descibed above in connection with controlling switch are also provided in con'- nection with controlling"switch 3 at station A, in connection with sw-itch2 ats-tation B; and again in connection with 's vitch 4' at station C.

Referring to the arrangements at station B, an additional battery 96 is provided thepositive pole of which is connected .to the windings ofthe solenoid 51 by a-wire 97, while the negative pole is connected to earth: 5 1, through wires 98, 52, and 53, preferably through a switch 99.- The thick wire winding of solenoid 51 is shown at 100 and the thinwire winding at 101, the former being connected by a wire 102 to the line wire 84, while the thin wire windinglOl is connected to the wire and thence to-the earth 54 through the upper contact 56-of'the solenoid core 50 and :wire 53 when the solenoid is energized.

- The positive pole of battery 96 is connected by a wire 103 to an outer-raillength 10 1 leading from branch'track 9 to the single tracksection X, the rail 10 1 being also connected :by a wire 105 to an outer rail length 306 of the branch track 107 leading from the single track section X to station 13, the two rails 10%. and 106 being carefully insulated from earth and from the adjacent rail lengths by track insulation of any-suitable kind, as shown. The inner'rail length 108 of branch track 9 and the inner length of rail 109 of branch track-107' are electrically connected together by a wire 110 and thence to earth at 111. Adjacent to the-arrival end of rail length 100 to be finally left by a train arriving at station B from station -A-is a short length of rail 112 which is insulated from earth andfrom the'rail length'106 by track insulation as shownyth'earrangement being such that as long as one Wheel of a vehicle axleisin contact with rail length 112 thewheel on the other end of the axle will be in contact with the earthed rail 109. The raillength 112 is electrically connected to. the line wire 84- by a wire 118, preferably through a switch 114k In describing the operation of the system itwill be supposedzthat a train is standing on branch track 5 at station A waiting for permission" to start towards station 13 and another train is standing on branch track 9 at station B waiting for permission to start towardsstation A, and the signalmenat stations A and B have agreed to despatch thefirst mentioned train first; The single'track section Xis clear and solenoids 39 and 51 are energized. The core 38 of solenoid 39 is held up by the current from battery 77 traversing the thin wire winding 82 and returning to the negative side of the battery through the upper contact 45 and wires 41%, 40 and 79, and through switch 80. The core 50 of solenoid 51 is held up by the current from battery 96 traversing the thin wire winding 101 and returning to the negative side of said battery through the upper contact 56 and wires 53, 52 and 98 and through switch 99. No current normally passes through the thick wire windings 81 and 100 of the respective solenoids 39 and 51 as these windings are connected in series with one another by the line wire 84 between the mutually opposing batteries 77 and 96 as seen in the diagram of Fig. 2.

The Signalman at A turns the switch 1 to the right to bridge the contacts 13 and 14, and the signalman at B turns the switch 2 to the left to bridge the contacts 22, 23. A current passes from the positive pole of battery through wire 36 and lower 0011- tact 37 of solenoid core 38 to contact'13 through blade of switch 1, contact 14, wire 17, trip coil 6, line wire 18, wire 57, contact 23, blade of switch 2, contact 22, wire 55, upper contact 56 of solenoid core 50, wire 53, to earth 5 1, and thence by earth 42 and wire to the negative side of battery Thus the trip coil 6 is energized, the trip is moved to safety position, the points are adjusted and the signal (not shown) lowered, and the train starts.

As soon as the front wheels of the train connect the insulated lengths of rails 88, 90, the battery 77 is short-circuited through the wires-85, 87, rails 88, 90, wire 91, earth 92, earth 12, wires 10 and 79 and switch 80. The solenoid is therefore (lo-energized and the core 38 drops, thus opening the circuit of the trip coil 6 at the lower contact 37.

The signahnen at A and 13 release their respective switches 1 and 2 and the train proceeds along the single track section X. In the meantime no further train movement in either direction between A and B can take place as both of the trips corresponding to coils 6 and 10 stand at danger position and neither the operating circuit of the one or the other can be closed until the solenoid 39 is again energized and the circuits again closed by the upper and lower contacts 15 and 37.

On the train approaching station B it passes to the branch track 107. On the .front wheels bridging the insulated rail lengths 106, 109 the battery 96 at station B is short circuited through wires 103, 105, rails 106, 109, wire 110, earths 111 and 54;, wires 52, 98 and switch 99. Hence the solenoid 51 is (ls-energized and its core 50 drops, thus opening the respective circuits controlled by the lower and upper contacts 49 and 56. If the train fails tov pass completely off rail length 106 the battery 96 remains short circuited and the switch 2 continues to be inoperative. On the last pair of wheels of the train passing from rails 106 and 109 and connecting rails 112 and 109 the said short circuit is broken and the circnit of the thick wire winding 100 of solenoid 51 is supplied with current as follows, from the positive pole of battery 96, through wire 97, winding 100, wire 102, switch 114,

wire 113, rail 112, rail 109, earths 111 and 5 1, wires 52,98 and switch 99, to the negative pole of the battery. On the core 50 being lifted the circuit of the thin wire winding 101 is completed to earth through the upper contact 56, the core 50 is maintained in raised position, and the circuit of the thick wire. winding 100 is again opened by the last pair of wheels of the train passing off the rail lengths 112 and 109.

At station 'A, as soon as the front pair of wheels of the train bridge the rails 112 and 109 the circuit of the thick wire winding 81 of the solenoid 39 is completed through wire 83,'line wire 81, switch 114, wire 113, rails 112 and 109, and earths 111, 12, back to the negative pole of battery 77. Hence the thick wire winding 81 of solenoid 39 is fully energized, the core 38 is raised and the maintaining circuit is closed through the thin wire winding 82, upper contact and wires 41, 40, 79 and switch 80; immediately afterwards the last wheels of the train pass off the rails 112 and 109, the thick wire winding 81 is again deprived of current, and the two switches 1 and 2 can again be operated to move the train waiting on track 9 from B to A.

For this purpose the signalman at B moves switch 2 tothe right and the signal man at A moves switch 1 to the left. A current passes from the positive pole of battery 4.7 through wire 18 and lower contact A9 of solenoid core 50 to contact 20, thence by blade of switch 2 to contact 21, through wire 19, trip coil 10, line wire 18, wire 46, contact 16, blade of switch 1, contact 15, wire 13, upper contact of solenoid core 38, wire 44, earths 42 and 5 1 and wire 52 back to the negative side of battery 47. The trip coil 10 is thus energized, the corresponding trip moves to safety position the points are adjusted and the starting signal (not shown) is lowered, and the train starts from B towards A. On the front wheels of the train engaging the insulated rail lengths 10s: and 108 the battery 96 is short-circuited through wire 103, rail 10 1, rail 108, wire 110, earths 111 and 54, wires 52, 98, and switch 99. Ihe solenoid 51 is therefore deenergized and its core drops thus rendering switch 2 inoperative for any further train movement over single track section X until the said solenoid is again energized. In the meantime the train proceeds along section X towards station A.

On the train approaching station A it passes to the branch track 7 and-on the front pair of wheels connecting rail lengths 86 and 89 the battery 77 is short-circuite'd through wire 85, rail 86', rail 89, wire 91,' earths 92 and 42, wires 10, 79, and switch 80. The solenoid 39 is therefore de-energized and drops its core 38, ensuring that switch 1 is inoperative as long as any part of the train is in contact with rails 86- and 89. On the last pair of wheels of the train leaving rails 86and 89 and connecting rails 93 and 89 the above short circuit is broken and the circuit of the thick wire winding 81 ofsolenoid 39 is .made through wire 78, winding 81, wire 83, switch 95, wire 94, rails 93 and 89, and earths-92 and 42 as previously. traced. The solenoid 39 is therefore again energized and lifts its core thus clos-' ing the local maintaining circuit through the thin wire winding 82 as before. The thick-wire winding 81 is again out out of operation when the last pair of wheels of the train passes off the rails '93 and 89.

At station B, as soon as the front pair of wheels of the train bridge the rails 93 and 89 the circuit of the thick wire winding'lOO of solenoid 51 is completed through wire 102, line wire 84: switch 95, wire 94:, rails 93 and 89, earths 92 and 5-1,wires 52, 98, and switch 99, back to the negative side of battery 96. The solenoid 51 being fully energized lifts its core 50and closes the local maintaining circuit through the thin wire winding 101 ashas been previously traced. On the last pair of wheels of the train. passing off the rails 93 and 89 the thickv wire winding 100 is again rendered currentless, and the two switches 1 and 2 can again be operated to effect a train movcnent over single track section X.

Referring to the dlagram in Fig. 2 it will be seen that on the solenoid core'38 dropping and opening contact 45, as a train starts from A towards B, the thick wire winding 81 of solenoid39 is connected between the battery'77 and earths 5 1 and 42 in series with the line wire 84:, the thick wire windinglOO and the thin wire winding' 1010f solenoid 51 at station B, as long as the solenoid 50 maintains the contact '56 closed. As the resistance of the thin wire winding of any one of the solenoids is several times as great. as that of the corresponding thick wire winding (and all the solenoids are of similar design), it will be clear to every electrician that it is quite easy to so design the solenoids that the winding 81, forv instance, \is unable to lift its core 38 under the conditions shown in Fig. 2 with thesame certainty as. if the circuitto earth from saidwindingwasopen, andin fact so .of station A that the said winding is only able to lift its core when the Y circuit toearth is closed either at 112 and 109, or at 93 and 89,"by the passage of a' train thus shunting the greater partof said resistance.

It is essential that a train arrivingat-station A from station B should pass completely clear of the insulated rails 93-and 89. Similarly, it is essential that a train-arriving at B from A should pass completely clear of the insulated-rails 112 and 109. Supposing for instance, thatthe last pairof wheels of a train on branch track 7 at A is bridging the rails 93 and 89, and a train is startedfrom' branch track 5 towards station B. Thelatter train on engaging the insulated rails88, 90 short circuits the battery 77 and tie-energizes the solenoid-39 in the manner described above. On the traincoinpletely clearing the said rails 88, 90 the solenoidv 39, would again be energized owing to the circuit of the thick wire winding 81 being completed through therear wheels of the train standing on track7. This may easilyjbe prevented from happening by arranging the track insulation in such a manner that a trainarriving on branch track'7 from station B must necessarily leave the rails 93, 89 to enable another train proceeding from A to B from track 5 to clear the rear vehicle of the train on. track 7. I Similarly in the case of the track insulation for rails 104, 106, 1108,; 109, 112, at station B, and at all other stations. i

1 The switches 80 and 99 are provided in the signal cabin to enable the signalman concerned to open the circuit of battery -77 c1196 in case he observes a trainor vehicle come to. a. standstill and likely to remain for some time in a position,short'circuiting the battery; thus these switches enable the signalmen to prevent unnecessary waste of current.

' .The switches 95 andll l givethe signal- .men control over the connections of the insulate'd' rails 93 and 112 with the line wire 84; andenable them to open said connections under certain irregular or unforeseen circumstances, such as, experience shows, will happen occasionally in the control-of railwayitrains. Forinstance, supposing a train has arrived from station B at'side track '7 and after having duly cleared the insulated rails 93' and 89 as described above a train is despatched from side track 5 at A towards B. If, while the latter train is proceeding along the single track section X, the train on track 7 is backed so as" to bridge the rails 93 and 89, this would have the effect of energiZ-ingthe solenoid'39 and thus interfering with the automatiocontrol thereof by the train proceeding to-B in the intendedmanner. If however the signal-man opens the switch 95-on observing, or perhaps authorizing, this backing movement :ofthe train on track 7 this interference with the intended automatic safety control is prevented, but without opening the saftey circuit from the thick wire winding 81 of solenoid 39, through Wire 83, line wire 84, Wire 118, rails 112, 109 at station B, toearth. Thus the intended operation of the system as regards a train proceeding from the station A, is in no way interfered with by the opening of the switch 95.

In addition to, or instead of, the provision of the switch 95, a simple automatic device of the kind shown in Fig. 3 may be provided adjacent to the rail 93, for example. This figure illustrates an automatic circuit-opener which is operated by a train. or vehicle when proceeding in one direction only, but is not affected by the vehicle moving thereover in the other direction. Referring to Fig. 3, a thin iron bar 115 is arranged on the inside of the track rail 116 adjacent to insulated rail 98 and is arranged at such a level that it is mechanically engaged by the flanges of the wheels of a train. The rail 116 is somewhat recessed on its inner side to enable the bar 115 to be forced into the recess as a train passes without appreciably altering the gauge of the track rails atthat point.

Th end 117 of the bar 115 is connected to a transverse bar 118 passing through a hole in the web of rail 116 and to the outer end of bar 118 one end of a tension spring 119 is secured the other end of the spring being fixed to the outer side of rail 116, the arrangement being adapted to normally maintain the end 117 of bar 115 such a distance, say 2% or 3 inches, away from the rail 116 that the flange of a wheel moving from left to right, will pass with certainty between the bar 115 and rail 116. The other end 120 of bar 115 is adapted normally to rest in the recess of the rail 11.6 after being once brought into this position by hand, and is connected to a short transverse bar 121 passinq through a hole in the web ofrail. 116. K flexible wire 122 is connected at one end to the transverse bar 121 and at the other end to the short arm 123 of a pivoted lever, the long arm 124 of which carries a movable contact 125 adapted normally to bridge the fixed contacts 126 inserted in the connection 941 (Fig. 1). An. off-centre tension spring 127 is connected between a fixed point 128 and the outer end of a third lever arm 129 fixed to, or integral with, the arms 123 and 124. The spring 127 is so arranged that when the contact 125 is bridging the contacts 126 the said spring passes to the right of thepivot of the levers 123, 124, 129, thus tending to maintain the contacts closed. At the same time the bar end 120 is drawn close against the rail 116 and the wire 122 is so adjusted that it has no undue slack in the said position of the parts.

It will be seen that as the wheels of 11 vehicle move over the device from right to left the flanges of the wheels force the bar 115 against the rail 116, the end 117 of the bar springing away from the rail to its normal position shown in the drawing after each wheel flange disengages therefrom. Thus the switch contact 125 is not affected thereby. If however a wheel of a vehicle moves over the device from left to right the wheel flange engages between the bar 115 and the rail 116 and forces the end 120 of bar 115-away from the rail 116; this movement is transmitted by the bar 121 and wire 122 to the short lever arm 123, thus rotating the device to open the contact 125. The device must be reset by hand.

The operation of the system between stations A and 0 being exactly similar to that above described for stations A and B, it is unnecessary to describe herein in detail the said operation between stations A and C as the circuits involved will be easily traced from the drawings.

lVhat I claim and desire to secure by Letters Patent is 1. For controlling the traffic on single track railways, the combination with the single track section and a signalling station at each end of the same, of an electrically controlled track device at each station governing the movementof the trains from the station on to the single track section, an operating circuit for each said track device comprising a line conductor connecting the two track devices, means for energizing one at a time the operating circuits to enabie a train to move from one station on to the single track section, an electromagnet at each station controlling the operating circuits, a connection to the track at each station for (ls-energizing the corresponding electromagnet on a train passing from the station on to the single track section, and a connection from the electromagnet through a second line conductor to the arrival track at the other station enabling the circuit of the said electromagnet to be again closed by the train on its arrival at the said other station.

2. For controlling the traffic on single track railways, the combination with a single track section and a signalling station at each end of the same, of a departure branch track and an arrival branch track at each station, an electrically controlled track device at each station governing the movement of trains from the departure branch track on to the singlctrack section, an operating circuit for each said track device comprising a line conductor connecting the two track devices, means for energizing one at a time the operating circuits to enable a train to move from the departure branch track at one station on to the singie track section, an electromagnet at each station controlling the 'operating circuits, said clec-troniagnet having two coils, one of 10W resistance referred to as the lifting coil and the other of relatively high resistance referred to as the maintaining coil, a source of current for the operating circuits, a separate source of current for energizing the controlling electromagnets, a connection from the energizing source of current to the de parture branch track at each station enabling said source of current to be short circuited on a train passing from the said branch track on to the single track section and consequently the operating circuits to be opened, and a connection from the energizing source of current through the lifting coil of the electroinagnet and a second line conductor to the arrival branch track at the other station causing the lifting circuit of the electromagnet to be again closed by the train on its arrival at the said other station.

3. For controlling the traffic on single track railways, the combination with a single track section and a signalling station at each end of the same, of an electrically controlled trip device at each station, means normally holding each trip device in its danger position, an operating circuit for each trip comprising a line conductor connecting the two trips, means for energizing one at a time the operating circuits to lower one trip to its safety position to alloW a train to pass from the corresponding sta tion on to the single track section, an electron'iagnet at each station controlling the operating circuits, a connection to the track at each station for de-energizing the corresponding electromagnet on a train passing from the station on to the single track section to cause the operating circuit to be opened and the trip device to return to its danger position, and a connection from the electromagnet through a second line conductor to the arrival track at the other station enabling the circuit of the said electromagnet to be again closed by the train on its arrival at the said other station to enable another train movement on to the singletrack section to take place.

4. For controlling the trafiic on single track railways, the combination With a single track section. and a signalling station at each end of the same, of electrically controlled track devices and operating circuits therefor for passing one train at a time on to the single track section, an electromagnct at each station controlling said circuits, connections to the track enablinga train to successively de-energize both electromagnets as it leaves one station and arrives at the other station, re-setting circuits for the two electromagnets, connections at each station to an insulated length of rail forming partof the re-setting' circuits to enable a train arriving at the station to close both resetting circuits in parallel, and means on the track to prevent the arriving train, after clearing the said insulated length of rail, from again closing the re-setting circuits by running back on to the, said insulated length of rail.

In testimony whereof I' have signed my name to this specification.

\VALT'ER JOHN UNDER- 00D. 

